Substrate holding apparatus and substrate processing method

The invention provides a retaining device of base plate and process method thereof for processing without vacuum adsorption base plates and process liquid dose not return to lower side of the base plates. The remaining device of base plate comprises: a bed plate (2) formed into a similar size with the base plate; a lateral wall (3) annually mounted above the bed plate; a support surface (24) which is formed above the lateral wall and supports radial inner part of external circumference under the base plate, and a non-contact surface (25) which is formed at external side of the support surface, lower than the support surface, and oppositely mounted with lower side of a part of radial external side of the base plate supported by the support surface; a gas supply pipe (14) formed on opening on the non-contact surface for supplying gas to clearances when process liquid processes upper surface of the base plate and preventing the process liquid from immersing into the clearances by using pressure thereof; and liqu